This invention relates to a method for rotational speed difference regulation of a switchable frictional engagement control.
According to the prior art an automatic transmission contains a hydrodynamic torque converter with converter lock-up clutch, at least one planetary set and two switchable frictional engagement controls in the form of a friction clutch or transmission brake, which serve to transmit torque.
Such frictional engagement controls are hydraulically closed. The opening as a rule is assisted by recoil springs. The arrangement of the components described allows a mechanical interruption of the drive train so that the input and output sides are entirely or also partly uncoupled. Said uncoupling divides the rotational speeds on the input from those on the output so that to a certain extent a torsional oscillation uncoupling is also possible.
In the present state of the art, frictional engagement controls (clutches, brakes) are used in the automatic transmission for different tasks or functions. One of the most important requirements in all clutch functions is to make possible in all driving modes a comfortable closing. It must here be ensured that the closing be comfortably secured over large rotational speed ranges of engine and output, the same as under different engine torques.
Furthermore, there are special operating modes where it is functionally necessary to adjust and maintain on one or more clutches or brakes defined rotational speed differences (slip). The driver must not feel as disturbing the transitions between the separate functions.
To satisfy said requirements, conventional solutions distinguish between different load states and depending thereon require changing parameters or even different control structures.
The Applicant""s DE 196 06 311 A1 discloses a closed lop control structure which based on a mathematical-physical model of the control system compensates in the form of a front-mounted correction member the essential non-linearities thus arriving in a control technical manner to a linear substitute control systems so that it be possible to use a simple linear governor to guide the controlled variable. Interferences such as outer torques acting upon the clutch are taken into account via a correction member.
One disadvantage of this method is the need of knowing a mathematical-physical path model, the quality of which directly influences the control quality attainable.
Therefore, this invention is based on the problem of indicating, on the basis of the cited prior art, a method for rotational speed difference regulation of a switchable frictional engagement control in a manner such that without knowing a mathematical-physical model the frictional engagement control so regulated takes over the transition between open and closed state, the same as the adjustment of a defined slip value, wherein the control design for each required utilization of the switchable frictional engagement control is identically constructed and takes care of an increased shifting and, driving comfort.
Besides, the inventive method should be utilizable for controlling any torque-transmitting clutches or brakes in the drive train. A linear governor must be used for this.
In addition the inventive method must take into consideration a prior existing knowledge of the path model but also in case of incomplete knowledge of the model ensure a sufficient sturdiness and control quality in all operating modes.
The method furthermore should allow a defined engine engagement for improving the control quality.
It is accordingly proposed, in a closed loop control for regulation of the rotational speed difference of a switchable frictional engagement control and specially of a clutch or of a brake, to provide with the desired rotational speed difference as reference input and the actual rotational speed difference as controlled variable, together with the clutch pressure to be adjusted, at least one other controlled variable and to provide the closed loop control with damping members so that the time shift of the damped variables per reading step does not exceed a predetermined value so that the exciting of the closed loop control remains in the stable range according to control technology.
According to the invention the engine torque is preferably used as added controlled variable.
It is also possible within the scope of the invention to take into account interferences, specially the actual turbine torque.
By using the inventive method the above mentioned disadvantages of the prior art appear no more. Besides, by virtue of he inventive total design switches of the control designs and regulating parameters are no longer needed.